JP2011187855A - Method of manufacturing multilayer ceramic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method, in which deterioration in varistor characteristic of a multilayer ceramic substrate having a cavity and a varistor function layer is prevented, and the warpage is prevented, and mounting of electronic components can be assured. <P>SOLUTION: In a process to bake a laminated body constituted by successively laminating: a first ceramic green layer 32; a varistor function green layer 34 used as the varistor function layer 14; a ceramic sinter substrate 31 used as a ceramic substrate 11; and a second ceramic green layer 33 used as the cavity, a baking contraction rate of the first ceramic green layer 32 is 0-40% at a baking contraction finish temperature of the second ceramic green layer 33, and the varistor function green layer 34 is baked at the baking contraction finish temperature of the first ceramic green layer 32 or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a multilayer ceramic substrate having a cavity and a varistor functional layer.

  With the development of blue light-emitting diode elements and the like, light-emitting diode elements, which are a type of semiconductor device, are expected to be widely spread from display devices to home lighting as compact, high-brightness, low-power-consumption light emitters.

  Conventionally, in order to use a light emitting diode element, a small and thin light emitting diode module in which the light emitting diode element is mounted on a multilayer ceramic substrate has been used. As shown in FIG. 3, the light emitting diode module uses an alumina ceramic substrate 51 having relatively good reflectivity and heat dissipation as a multilayer ceramic substrate in order to increase the reflectance of the light emitting diode element 50 and prevent a decrease in light emission efficiency due to heat generation. A cavity 52 used for condensing light is provided on the upper surface. Further, it is performed that a thermal via (not shown) is passed through the ceramic substrate 51 to further improve heat dissipation.

  Further, in order to protect the light emitting diode element 50 against surge voltage such as electrostatic discharge, a varistor function layer 55 is provided on the lower surface of the ceramic substrate 51, and the varistor is interposed between the connection vias 53, 54 of the power supply line of the light emitting diode element 50. The functional layer 55 is electrically connected to take measures against static electricity. In this multilayer ceramic substrate, a glass ceramic green layer to be a glass ceramic layer 56, a varistor functional green layer to be a varistor functional layer 55, a sintered substrate to be a ceramic substrate 51, and a ceramic green layer to be a cavity 52 are sequentially provided and fired. Is formed.

  As prior art document information relating to the invention of this application, for example, those shown in Patent Document 1 and Patent Document 2 are known.

JP 2005-209663 A JP 2008-270325 A

  However, such a conventional multilayer ceramic substrate has the same glass ceramic composition as the glass ceramic layer 56 as the cavity 52 in order to shorten the firing time and increase the production efficiency. There is a problem that the warp of the multilayer ceramic substrate is increased due to the firing shrinkage difference of each layer of the ceramic substrate, and the mountability of the light emitting diode element 50 is deteriorated. Further, if the glass ceramic green layer to be the glass ceramic layer 56 is made thin in order to suppress warpage, there is a problem that the varistor characteristics deteriorate during firing or in a high temperature and high humidity environment.

  The present invention solves the above-described conventional problems, and provides a method for manufacturing a thin multilayer ceramic substrate excellent in electronic component mountability by suppressing warpage while preventing deterioration of varistor characteristics. .

  In order to achieve the above object, the present invention provides a method for manufacturing a multilayer ceramic substrate having a cavity surrounding an electronic component mounting portion on an upper surface, comprising a first ceramic green layer, a varistor function green layer, a ceramic firing layer. A step of firing a laminated body in which a bonded substrate and a second ceramic green layer serving as the cavity are sequentially laminated, and in the firing, the firing shrinkage ratio of the first ceramic green layer is the second ceramic green This is a method for producing a multilayer ceramic substrate in which the varistor function green layer is fired at a firing shrinkage completion temperature of the layer of 0% to 40% or higher than the firing shrinkage completion temperature of the first ceramic green layer.

  As described above, according to the present invention, in a thin multilayer ceramic substrate having a cavity and a varistor functional layer, it is possible to prevent warping while preventing deterioration of varistor characteristics and to secure the mountability of electronic components.

Sectional drawing of the light emitting diode module in embodiment of this invention The principal part perspective view of the laminated body which shows the lamination process of the laminated body in embodiment of this invention and becomes a multilayer ceramic substrate Cross-sectional view of a conventional light emitting diode module

(Embodiment)
A multilayer ceramic substrate according to an embodiment of the present invention will be described.

  The multilayer ceramic substrate of the present embodiment is a multilayer ceramic substrate for a light emitting diode module on which a light emitting diode element 28 is mounted as an electronic component as shown in FIG. The multilayer ceramic substrate has a ceramic substrate 11, and a mounting portion 20 is provided at the center of the upper surface 18 of the ceramic substrate 11. The ceramic substrate 11 is based on an insulating sintered body mainly composed of aluminum oxide, aluminum nitride or the like, and is provided on a flat plate having a square shape or a circular shape.

  The thickness of the ceramic substrate 11 is preferably 150 μm to 500 μm or less in order to reduce the thickness of the multilayer ceramic substrate.

  The mounting portion 20 is formed with a pair of mounting electrodes 21 and 22 formed on the surface of the upper surface 18 of the ceramic substrate 11, and the mounting electrodes 21 and 22 are joined to terminal electrodes of the light emitting diode element 28 via bumps or the like. The mounting electrode 21 and the mounting electrode 22 are formed in different areas corresponding to the shape of the terminal electrode of the light emitting diode element 28, and the mounting electrode 22 is provided in a larger area.

  Further, a cavity 29 surrounding the mounting portion 20 is laminated on the upper surface 18 of the ceramic substrate 11, and the cavity 29 is formed of the second ceramic layer 13 and is provided outside the outer periphery of the light emitting diode element 28 in a plan view and accommodates the light emitting diode element 28. To do. Further, the side surface of the cavity 29 surrounding the mounting portion 20 is provided on a vertical surface or an inclined surface extending upward with respect to the ceramic substrate 11. Further, the second ceramic layer 13 is not formed on the mounting portion 20 on the upper surface 18 of the ceramic substrate 11.

  A varistor functional layer 14 laminated on the lower surface 19 of the ceramic substrate 11 is provided on the bottom surface side of the multilayer ceramic substrate. The varistor functional layer 14 is formed by alternately laminating varistor layers 15 and internal electrodes 16 and 17. Is at least partially sandwiched between a pair of internal electrodes. One internal electrode 17 is formed on the lower surface 19 of the ceramic substrate 11.

  Further, the multilayer ceramic substrate has a first ceramic layer 12 laminated on the lower surface of the varistor function layer 14, and one surface of the first ceramic layer 12 is exposed and serves as a bottom surface of the multilayer ceramic substrate. The first ceramic layer 12 serves as an insulating protective layer for electrically insulating the circuit board on which the multilayer ceramic substrate is mounted from the varistor function layer 14.

  A pair of terminal electrodes 23 and 24 formed on the surface of the first ceramic layer 12 are provided on the bottom surface of the multilayer ceramic substrate, and the pair of terminal electrodes 23 and 24 and the pair of mounting electrodes 21 and 22 are The multi-layer ceramic substrate is electrically connected via a pair of connection vias 25 and 26 embedded in the thickness direction, and the connection vias 25 and 26 are further electrically connected to the internal electrodes 16 and 17 of the varistor function layer 14, respectively. It is connected.

  The thermal via 27 is provided through the ceramic substrate 11 in order to improve heat dissipation of the light emitting diode element 28 which is a heat generating component. The upper end portion 27 a of the thermal via 27 is disposed immediately below the mounted light emitting diode element 28 and is joined to the mounting electrode 22, and the lower end portion 27 b is connected to one internal electrode 17 electrically connected to the mounting electrode 22. Connected. Thus, by connecting the lower end portion 27b of the thermal via 27 to the internal electrode 17 and not exposing the bottom surface of the multilayer ceramic substrate, it is possible to ensure heat dissipation and mountability when the multilayer ceramic substrate is mounted on a motherboard substrate or the like. it can.

  Thus, since the mounting part 20 is provided on the opposite side to which the varistor function layer 14 and the first ceramic layer 12 are provided, the heat of the mounted light-emitting diode element 28 is thermally conductive without hindering heat conduction. It is possible to dissipate efficiently to the high ceramic substrate 11.

  As shown in FIG. 2, the multilayer ceramic substrate manufacturing method includes a first ceramic green layer 32 to be the first ceramic layer 12, a varistor functional green layer 34 to be the varistor functional layer 14, and a ceramic to be the ceramic substrate 11. After the sintered body substrate 31 and the second ceramic green layer 33 to be the cavity 29 are sequentially laminated to form a laminated body, the laminated body is baked and integrated.

  In the step of forming the laminated body, the second ceramic green layer 33 is laminated on the ceramic sintered body substrate 31 so as to surround the periphery of the mounting portion 20 on the upper surface 18 of the ceramic substrate 11 of the multilayer ceramic substrate.

  In the step of sintering the laminated body, the temperature is increased at a predetermined temperature increase rate, and then held at the highest firing temperature for a certain time. The firing temperature is set to a temperature suitable for firing the varistor function green layer 34 above the firing shrinkage completion temperature of the first ceramic green layer 32.

  In the firing step, the main body of the ceramic sintered body substrate 31 is not substantially fired, so that the second ceramic green layer 33 contacting the ceramic sintered body substrate 31 is restrained from firing shrinkage by the ceramic sintered body substrate 31. The

  The firing shrinkage ratio of the first ceramic green layer 32 is 0% to 40% at the firing shrinkage completion temperature of the second ceramic green layer 33. By using this firing shrinkage ratio, deterioration of the varistor characteristics can be prevented. Even if the ceramic substrate 11 is made thinner than the thickness of the first ceramic layer 12 provided, the warp of the multilayer ceramic substrate can be suppressed and the mountability of the electronic component can be secured.

  When the firing shrinkage ratio of the first ceramic green layer 32 is larger than 40%, the balance of the shrinkage stress acting on the upper surface and the lower surface of the ceramic sintered body substrate 31 is increased by the shrinkage of the first ceramic green layer 32. For this reason, the amount of warpage of the multilayer ceramic substrate increases, and the mounting defects of electronic components such as light emitting diode elements on the multilayer ceramic substrate increase remarkably.

  The firing shrinkage ratio of the first ceramic green layer 32 is more preferably 0% to 5%, the influence of shrinkage variation of the first ceramic green layer 32 can be reduced, and the multilayer ceramic having the cavity 29 and the varistor function layer 14. It is possible to prevent the mounting failure of the substrate.

  Thus, in order to control the firing behavior of the first ceramic green layer 32 and the second ceramic green layer 33, the first ceramic layer 12 and the second ceramic layer 13 can be fired at a relatively low temperature. It is preferable to use glass ceramic powder as a main component.

  The thickness of the first ceramic green layer 32 is preferably 5 μm to 50 μm, and the multilayer ceramic substrate can be made thin, and the varistor material of the varistor green layer 35 that becomes the varistor layer 15 when fired by the first ceramic green layer 32. Thus, the varistor characteristics can be prevented from being deteriorated in the high temperature and high humidity environment by the first ceramic layer 12 after firing.

  Further, when holding at the firing temperature, the varistor function green layer 34 is sandwiched between the ceramic sintered body substrate 31 and the first ceramic green layer 32 that has undergone the firing shrinkage, so that the firing shrinkage is restricted. The warpage of the laminate due to the functional green layer 34 is suppressed.

  Here, the firing shrinkage ratio at a predetermined temperature indicates the ratio of the firing shrinkage amount to the entire firing shrinkage amount in the thickness direction when a single green sheet is heated from room temperature to the firing temperature at a temperature rising rate of 5 ° C./min. The shrinkage completion temperature is a temperature at which the firing shrinkage ratio is 99% or more.

(Example)
Next, the manufacturing method of the multilayer ceramic substrate of the Example of this invention is demonstrated using FIG. 1, FIG.

  First, a ceramic sintered substrate 31 of aluminum oxide having a thickness of 280 μm and a purity of 95% or more is prepared as a substrate body of the ceramic substrate 11.

  Subsequently, a varistor function green layer 34 having a thickness of 20 μm is formed on the lower surface 19 with the lower surface 19 of the ceramic sintered body substrate 31 facing upward. The varistor function green layer 34 is produced by alternately laminating conductor layers 36 and 37 to be the internal electrodes 16 and 17 and the varistor green layer 35 by screen printing. One conductor layer 37 is laminated on the surface of the ceramic sintered body substrate 31 so as to be formed on the lower surface 19 of the ceramic substrate 11.

  The conductor layers 36 and 37 are formed in a rectangular pattern using a metal paste of Ag / Pd powder, and the varistor green layer 35 is mainly composed of zinc oxide and is made of bismuth oxide, manganese oxide, cobalt oxide, antimony oxide, or the like. It is formed using a paste containing a varistor powder obtained by adding a subcomponent to zinc oxide.

  Further, an intermediate laminate in which the first ceramic green layer 32 is formed on the varistor function green layer 34 by screen printing, and the first ceramic green layer 32, the varistor function green layer 34, and the ceramic sintered body substrate 31 are sequentially laminated. Get.

  The first ceramic green layer 32 is formed using a ceramic paste containing glass ceramic powder, and the glass ceramic powder is mainly composed of silicon oxide, aluminum oxide, and magnesium oxide, and barium oxide and calcium oxide as subcomponents. As added. The first ceramic green layer 32 has a thickness of 30 μm so as to prevent deterioration of the varistor characteristics.

  At this time, connection vias 38 and 39 having a diameter of 150 μm are formed in the intermediate laminate so as to penetrate the intermediate laminate, and a thermal via 40 having a diameter of 200 μm is formed so as to penetrate the ceramic sintered body substrate 31. The connection vias 38 and 39 and the thermal via 40 are formed by filling an Ag / Pd paste fired at a temperature lower than the firing temperature of the varistor function green layer 34 by screen printing or the like.

  Next, Ag / Pd paste is applied to the top and bottom surfaces of the intermediate laminate by screen printing to form conductor layers for the mounting electrodes 21 and 22 and the terminal electrodes 23 and 24.

  Further, a second ceramic green layer 33 is laminated on the upper surface of the ceramic laminate substrate 31 of the intermediate laminate to obtain a laminate. During the lamination, the second ceramic green layer 33 surrounds the periphery of the mounting portion 20 on the upper surface of the ceramic substrate 11 of the multilayer ceramic substrate and has a constant width of 100 μm along the outer periphery of the ceramic substrate 11. The green layer 33 is formed on the ceramic sintered body substrate 31. The thickness of the second ceramic green layer 33 is preferably 150 μm to 500 μm so as to be a cavity.

  The second ceramic green layer 33 is formed by adding an organic binder and an organic solvent to glass ceramic powder to produce a ceramic paste, and applying and drying the ceramic paste on the ceramic sintered body substrate 31 by screen printing. Is done. As the glass ceramic powder of the ceramic paste of the second ceramic green layer 33, a mixture of silicon oxide and zinc oxide as main components and an alkaline earth metal oxide as a subcomponent is used.

  The first ceramic green layer 32, the varistor green layer 35, and the second ceramic green layer 33 may be formed using a green sheet molding method or the like.

  Next, the laminated body is heated and fired at 800 ° C. to 1100 ° C. in the atmosphere to obtain a ceramic sintered body of a multilayer ceramic substrate aggregate in which a plurality of multilayer ceramic substrates are provided in a lattice shape.

  Subsequently, after the conductive layers for the mounting electrodes 21 and 22 and the terminal electrodes 23 and 24 of the multilayer ceramic substrate assembly are plated with Ni, Pd, Au, etc., the mounting electrodes 21 and 22 and the terminal electrodes 23 and 24 are obtained. Then, the multilayer ceramic substrate aggregate is cut into a lattice shape and separated to obtain a chip-shaped multilayer ceramic substrate having a width of 1.6 mm and a length of 0.8 mm.

  Here, the multilayer ceramic substrate in which the firing shrinkage ratio of the first ceramic green layer 32 is 0%, 5%, 20%, 40%, 60%, 100% at the firing shrinkage completion temperature of the second ceramic green layer 33. Samples No. 1 and No. 2 were prepared. 1-No. It was set to 6.

  Next, the average value of 30 samples of each sample No. was calculated for the amount of warpage of the multilayer ceramic substrate. Moreover, the mounting defect rate of the light emitting diode element to the multilayer ceramic substrate was evaluated.

  The results are shown in (Table 1).

  As shown in (Table 1), at the temperature at which the second glass ceramic is completely fired and contracted, the first glass ceramic has a firing shrinkage ratio of 0% to 40%. 1 to Sample No. For No. 4, the mounting failure rate of the light-emitting diode element was 1% or less and the mounting property was good, but when the firing shrinkage ratio exceeded 40%, the mounting failure rate was remarkably deteriorated. In particular, when the firing shrinkage ratio was 0% to 5%, no mounting failure occurred.

  In the case where electronic components are mounted using a multilayer ceramic substrate assembly instead of a single multilayer ceramic substrate, the warp of the multilayer ceramic substrate assembly can be suppressed to ensure mountability.

  The multilayer ceramic substrate of the present invention has the effect of suppressing the warpage while preventing the deterioration of the varistor characteristics of the substrate provided with the cavity and the varistor functional layer and ensuring the mountability of the electronic component. Useful for ceramic substrates.

DESCRIPTION OF SYMBOLS 11 Ceramic substrate 12 1st ceramic layer 13 2nd ceramic layer 14 Varistor functional layer 15 Varistor layer 16, 17 Internal electrode 20 Mounting part 25, 26 Connection via 27 Thermal via 28 Light emitting diode element 29 Cavity 31 Ceramic sintered body substrate 32 First ceramic green layer 33 Second ceramic green layer 34 Varistor functional green layer 35 Varistor green layer 36, 37 Conductor layer 38, 39 Connection via 40 Thermal via

Claims (3)

A method of manufacturing a multilayer ceramic substrate having a cavity surrounding an electronic component mounting portion on an upper surface, the first ceramic green layer, a varistor function green layer, a ceramic sintered body substrate, and a second cavity serving as the cavity And a step of firing a laminate in which the ceramic green layers are sequentially laminated. In the firing, the firing shrinkage ratio of the first ceramic green layer is 0% to 40 at the firing shrinkage completion temperature of the second ceramic green layer. %, And the varistor functional green layer is fired at a temperature equal to or higher than the firing shrinkage completion temperature of the first ceramic green layer. The method for producing a multilayer ceramic substrate according to claim 1, wherein the firing shrinkage ratio of the first ceramic green layer is 0% to 5% at the firing shrinkage completion temperature of the second ceramic green layer. The method for producing a multilayer ceramic substrate according to claim 1 or 2, wherein the first ceramic green layer and the second ceramic green layer use glass ceramic powder as a main component.

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